UNIT 14 IMFs, LIQUIDS, SOLIDS PACKET. Name: Date: Period: #: BONDING & INTERMOLECULAR FORCES

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1 Name: Date: Period: #: BONDING & INTERMOLECULAR FORCES p. 1

2 Name: Date: Period: #: IMF NOTES van der Waals forces: weak attractive forces between molecules. There are 3 types: 1. London Dispersion Forces (LDF)- these are the weakest interactions; caused by the motion of electrons. Non-polar molecules have only these forces. Everything with electrons has LDF. 2. Dipole-dipole interaction (polar molecules)-attraction between the positive portion of one molecule and the negative part of another molecule. 3. Hydrogen bonds-(strong type of dipole-dipole interaction) attractive forces in which a hydrogen covalently bonded to a very electronegative atom (N, O, F) is also weakly bonded to an unshared pair of electrons of another electronegative atom on an adjacent, neighboring molecule. Examples: H2O, NH3, HF, alcohols (CH3OH), amines (CH3NH2) Hydrogen bonding gives water an unusually high boiling point for its mass and causes it to expand as it freezes (ice is less dense than liquid water). From weakest to strongest intermolecular force: London Dispersion forces < Dipole-dipole interactions < Hydrogen bonding * * * * * * * * * * * * * * Regarding van der Waal Forces: Whether a substance exists as a solid, liquid, or gas depends on the relationship between kinetic energy and attractive forces and which one dominates. 1. Long skinny molecules tend to have stronger dispersion forces than short fat ones due to increased surface area. n-pentane bp 309.4K neo-pentane bp 282.7K 2,2-dimethylpropane 2. Strength increases with increasing molecular weight (molar mass). Larger atoms have larger electron clouds and are easier to polarize. Which one has the highest boiling point? He, Ne, Ar, Kr, Rn 3. For two molecules of similar size and shape, dipole-dipole interactions have a greater effect than LDF on physical properties. For the two molecules below, which one has the lower boiling point? OR 4. If one molecule is much larger than another, LDF will be more important in determining physical properties. For example, C 25 H 52 is a formula for candle wax, a solid at room temperature. H 2 O, water, is a liquid at room temperature. 5. Increased strength of attractive forces causes lower equilibrium vapor pressure, increased boiling point, increased melting point, and increased heats of vaporization and fusion. p. 2

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8 Name: Date: Period: #: EXTRA LIQUID NOTES Vapor pressure the pressure exerted by vapor molecules of the surface of a liquid at equilibrium - Measured in a closed system where rate of evaporation = rate of condensation - Vapor pressure is directly related to the temperature of the liquid (see graph below) Boiling point temperature at which the vapor pressure of the liquid equals the pressure of its environment (typically standard pressure, 1 atm) - Below 1 atm of vapor pressure, no bubbles of vapor can form because the pressure on the surface of the liquid is greater than the pressure in any spaces in the liquid where bubbles are trying to form. - A normal boiling (or melting) point indicates that the pressure of the system is 1 atm. - Volatile is a word used to describe liquids that readily evaporate due to weak IMFs. Cohesive forces IMFs between neighboring molecules of the liquid Adhesive forces IMFs between liquid molecules and their container - The degree of attraction is based on polarity of substances. - These forces explain: Formation of menisci: concave versus convex Capillary action: the spontaneous rising of a liquid in a narrow tube Let s also not forget that IMFs explain viscosity and surface tension in liquids! IMFs EXPLAIN SO MUCH!!! But please don t confuse IMFs for ionic or covalent bonds p. 8

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10 Name: Date: Period: #: SOLIDS NOTES I. Crystalline vs. Amorphous II. Unit cell (cubic) a. The cube: How many present in a cube Portion of atom inside unit cell Corner 8 1/8 of atom Center of cube 1 1 atom Face 6 1/2 of atom Edge 12 1/4 of atom i. primitive ii. body-centered iii. face-centered III. Molecular solids a. Molecular b. Covalent-Network c. Ionic d. Metallic p. 10

11 Name: SEMICONDUCTORS WS #: Directions: This is a digital copy of this worksheet that you have in hard copy. Please follow the directions on this handout, answering any questions on this hard copy worksheet as you go. Use the digital copy so that you can quickly click on the needed internet links. Video #1: Semi-Conductors: 3D animation Click on the following link to watch the video clip. 1) How many atoms does a silicon atom bond to? 2) At zero kelvin, silicon does not conduct. However, when heat is added it will conduct. How does adding heat cause silicon atoms to conduct electricity? Video #2: How Does a Transistor Work? Click on the following link to watch the video clip. N-type Semiconductors: Doping silicon with phosphorus creates an n-type semi-conductor. The n in n-type stands for negative, but it does not mean that the semi-conductor is negative in charge. 3) What does the term, n-type, tell you about the semi-conductor? 4) Why does doping with phosphorus create an n-type semi-conductor? P-type Semi-conductors: Doping with boron creates a p-type semi-conductor. The p in p-type stands for positive, but it does not mean that the semi-conductor has a positive charge. 5) What does the term, p-type, tell you about the semi-conductor? 6) Why does doping with boron create a p-type semi-conductor? Transistors: Transistors consist of n-type and p-type semi-conductors. At the right, is a diagram similar to the transistor discussed in the video. 7) Why don t electrons flow through the transistor when no voltage is applied at the gate? (Please mention depletion layer ) 8) Why do electrons flow through the transistor once a positive voltage is applied at the gate? 9) Why is there a limit for how close the transistors can be to each other? p. 11

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15 Name: Date: Period: #: LIQUIDS & SOLIDS REVIEW 1. As the strength of attractive forces increases, which of the following would increase? Melting point deviations from ideal gas law Boiling point enthalpy of fusion Viscosity enthalpy of vaporization Equilibrium vapor pressure 2. List examples of intermolecular forces: 3. List examples of intramolecular forces: 4. What two processes occur at the same rate and at the same time to produce equilibrium vapor pressure? 5. How would you characterize: Ionic compounds? Network covalent compounds? Molecular solids? Metallic compounds? 6. Describe capillary action: 7. On page 455, determine the boiling point at 400 torr of diethyl ether? Ethanol? 8. What is the difference between an amorphous solid and a crystalline solid? DIRECTIONS FOR BACK: For each of the following, indicate the state of matter at room temperature and all the types of attractive forces present. For solids, indicate if they are network covalent, ionic, metallic, or molecular. Remember molecular solids will also have IMFs present between the molecules. Liquids and gases will only have IMFs. p. 15

16 Name: Date: Period: #: SUBSTANCE STATE OF MATTER ATTRACTIVE FORCES 13. diamond 14. KNO3 15. SiO2 16. Cl2 17. NaCl 18. Na sodium 19. Cu copper 20. NaNO3 21. CH4 22. glycerine C3H5(OH)3 liquid polar covalent molecular, hydrogen bonding 23. I2 24. CO2 25. Ne 26. C2H6 27. N2 28. HF 29. H2O 30. NH3 31. Na2S 32. F2 33. Br2 34. Ag silver 35. CH3OH 36. C2H5OH p. 16